Difference
between red and yellow tomatoes. Extracted this from eHow.com

The most obvious difference between these two types of
tomato is their color. Red tomatoes are far more common than yellow tomatoes,
and are often the only color of tomato found in grocery stores and
supermarkets. Red tomatoes are high in lycopene, a powerful antioxidant thought
to prevent some cancers. Lycopene is what produces the tomatoes' red color.
Yellow tomatoes do not contain lycopene. Red tomatoes are highly acidic, which
produces their tangy flavor. Yellow tomatoes are lower in acidity, making them
generally sweeter than red tomatoes. Red tomatoes are higher in vitamin C,
while yellow tomatoes are higher in niacin and folate. Both colors are a tasty and
nutritious addition to any meal.